1. Field of the Invention
This invention relates to a polyorganosiloxane compound characterized by containing in the molecule both a silicone oil chain structure and a silicone resin structure having an alkoxyl group and/or a silanol group, and also relates to a coating composition making use of this compound. More particularly, this invention relates to a novel polyorganosiloxane compound which is compatible with silicone resins, and a coating composition making use of this compound.
2. Description of the Prior Art
Nowadays, silicone resins are widely used in various fields because of their superior properties in respect of water repellency, heat resistance, weatherability, freeze resistance, electrical insulation properties, chemical resistance and safety to the human body.
Among them, silicone resins having a three-dimensional cross-linked structure composed chiefly of SiO2 units (Q units) and RSiO1.5 units (T units; R is an organic group such as an alkyl group or a phenyl group) are widely used in coating materials and binders, using their curability. In particular, a liquid substance having an Sixe2x80x94OR group as a cross-linking group is, as disclosed in Japanese Patent No. 2137192, utilized as a chief ingredient of a solvent-free type coating material which is combustible and does not contain any organic solvent harmful to the human body. Also, there is an advantage that this Sixe2x80x94OR group is not required to be heated to cure because of its cross-linking reaction which proceeds by moisture in air and at room temperature and hence any coating materials making use of this substance as a chief ingredient can be applied in situ.
Such a Sixe2x80x94OR type silicone resin has strong points of good curability and high surface hardness because of its three-dimensional cross-linked structure. It, however, affords an insufficient flexibility to cause cracks in coating films in some cases. In order to improve this flexibility, a method has been employed in which diorganosiloxane (R2SiO) units (D units) are incorporated when the silicone resin is synthesized. In this case, however, the D units are incorporated in the structure at random, and hence there is a problem that, the D units must be added in a large quantity in order to impart the flexibility, so that the superior curability and surface hardness, the strong points of this silicone resin, may lower.
In addition, the D units are added to the silicone resin in the form of chain structure. Hence, in an attempt to add a silicone oil comprised of chain structure of D units, its addition may cause milkiness or repellency of coating films because of a poor compatibility of the silicone oil with the silicone resin. Thus, it can not be added as what is expected of itself.
A method of adding a silicone oil terminated with TEOS (Si(OEt)4) at both terminals of the molecular chain is also proposed (Polymeric Materials Science and Engineering, 1998, Vol.79, 192). In this case, too, its compatibility with silicone resins is not improved, and its addition causes milkiness or repellency of coating films.
It is also possible to improve the flexibility by adding to the silicone resin a resin other than silicone, such as acrylic resin or epoxy resin. However, these resins commonly have weatherability and so forth which are inferior to those of silicone, so that the resultant coating material has low weatherability and so forth.
Accordingly, an object of the present invention is to provide a polyorganosiloxane compound having a specific structure, which is compatible with silicone resins.
Another object of the present invention is to provide a coating composition which utilizes this polyorganosiloxane compound and can obtain coatings improved in flexibility without lowering the properties inherent in silicone resins, such as curability, surface hardness and weatherability.
In order to achieve the above objects, the present inventors have made extensive studies and have accomplished the present invention.
More specifically, firstly, the present invention provides a polyorganosiloxane compound which contains in the molecule a silicone oil structure and a silicone resin structure having at least one of an alkoxyl group and a silanol group and is compatible with a silicone resin:
The compound is obtained by allowing the following polyorganosiloxane (a1) to react with the following polyorganosiloxane (a2) in the presence of a hydrosilylation catalyst.
(a1) A polyorganosiloxane represented by the average compositional formula (1):
xe2x80x83R1aR2bSi(OR3)cO(4xe2x88x92axe2x88x92bxe2x88x92c)/2xe2x80x83xe2x80x83(1)
xe2x80x83wherein R1 is at least one group selected from the group consisting of a substituted or unsubstituted alkyl group and a substituted or unsubstituted aryl group; R2 is a group containing an aliphatic unsaturated double bond; R3 is at least one member selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms which may have an ether linkage; and a, b and c are numbers that satisfy the following relation: 0xe2x89xa6a less than 1.5, 0.01xe2x89xa6bxe2x89xa61, 0.5xe2x89xa6a+bxe2x89xa61.8, 0.01xe2x89xa6cxe2x89xa62.5 and 1xe2x89xa6a+b+cxe2x89xa63; and having at least one aliphatic unsaturated double bond in the molecule.
(a2) A polyorganosiloxane represented by the general formula (2): 
xe2x80x83wherein R1 is as defined in respect of the above formula (1), and n is a number of from 0 to 1,000.
Secondly, the present invention provides a coating composition comprising:
(xcex1) from 0.1 part by weight to 100 parts by weight of the polyorganosiloxane compound described above;
(xcex2) from 99.9 parts by weight to 0 part by weight of a silane compound and/or silicone resin containing an R3Oxe2x80x94Si group where R3 is as defined above;
provided that the total of components (xcex1) and (xcex2) comes to 100 parts by weight; and
(xcex3) from 0.01 part by weight to 50 parts by weight of a curing catalyst, based on 100 parts by weight of the total of the components (xcex1) and (xcex2).
The present invention is described below in detail.
Polyorganosiloxane Compound
The polyorganosiloxane compound of the present invention which contains in the molecule a silicone oil structure (straight-chain siloxane structure) and a silicone resin structure (branched siloxane structure) having at least one of an alkoxyl group and a silanol group and is compatible with a silicone resin (comprised of a branched siloxane structure). This polyorganosiloxane compound may be produced by a process including, but not particularly limited to, the following two processes.
The first process utilizes the reaction of hydrosilylation of Sixe2x80x94H groups to aliphatic unsaturated double bonds, and comprises allowing a polyorganosiloxane (a1) represented by the following average compositional formula (1), with a polyorganosiloxane (a2) represented by the following general formula (2).
R1aR2bSi(OR3)cO(4xe2x88x92axe2x88x92bxe2x88x92c)/2xe2x80x83xe2x80x83(1)
wherein R1 is at least one group selected from the group consisting of a substituted or unsubstituted alkyl group and a substituted or unsubstituted aryl group; R2 is a group containing an aliphatic unsaturated double bond; R3 is at least one member selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms which may have an ether linkage; and a, b and c are numbers that satisfy the following relation: 0xe2x89xa6a less than 1.5, 0.01xe2x89xa6bxe2x89xa61, 0.5xe2x89xa6a+bxe2x89xa61.8, 0.01xe2x89xa6cxe2x89xa62.5 and 1xe2x89xa6a+b+cxe2x89xa63; and having at least one aliphatic unsaturated double bond in the molecule. 
wherein R1 is as defined in respect of the above formula (1), and n is a number of from 0 to 1,000.
Polyorganosiloxane (a1):
This polyorganosiloxane (a1) is chiefly composed of R1SiX3 and R2SiX3, and is obtained using as a starting material at least one of SiX4, R12SiX2, R13SiX, R22SiX2 and R23SiX [where R1 and R2 are as defined in respect of the formula (1); X represents in the present specification a hydrolyzable group as exemplified by a halogen atom or an xe2x80x94OR3 group; and R3 is as defined in respect of the formula (1)] in accord with the desired structure, and by hydrolysis and condensation with addition of a solvent and an alcohol (R3OH, where R3 is as defined above), under acidic or alkaline conditions and using water in a quantity smaller than that of water in reaction equivalent weight for the hydrolyzable group X. This compound is known to those skilled in the art, as ROxe2x80x94Si-group-containing silicone resin.
The group represented by R1 in the average compositional formula (1), is at least one group selected from the group consisting of a substituted or unsubstituted alkyl group and a substituted or unsubstituted aryl group. It may specifically include alkyl groups having 1 to 20 carbon atoms, such as a methyl group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group and an i-butyl group; aryl groups having 6 to 20 carbon atoms, such as a phenyl group; and groups containing a substituent such as a trifluoropropyl group, a 3-aminopropyl group, a 3-glycidoxypropyl group or a 3-mercaptopropyl group. In view of availability, curability required when the polyorganosiloxane compound of the present invention is added to the silicone resin, and weatherability, a methyl group is particularly preferred.
Letter symbol a, which represents the number of R1, is a number within the range of 0xe2x89xa6axe2x89xa61.5. If a greater than 1.5, the curability required when the polyorganosiloxane compound is added to the silicone resin and the resultant coating film hardness may be insufficient. Also, letter symbols a, b and c are numbers that satisfy 0.01xe2x89xa6bxe2x89xa61, 0.5xe2x89xa6a+bxe2x89xa61.8, 0.01xe2x89xa6cxe2x89xa62.5 and 1xe2x89xa6a+b+cxe2x89xa63.
The group represented by R2 is a group having an aliphatic unsaturated double bond, where at least one group must be present in the molecule in order to allow the polyorganosiloxane (a1) to react with the polyorganosiloxane (a2). As specific examples of this group having such an unsaturated double bond, it may include aliphatic groups such as a vinyl group, an allyl group, an isopropenyl group, a 1-butenyl group, a 2-butenyl group and a 3-butenyl group; alicyclic groups such as a 2-cyclohexenyl group, a 3-cyclohexenyl group, a 2-vinylcyclohexyl group, a 3-vinylcyclohexyl group and a 4-vinylcyclohexyl group; aromatic groups such as a 2-vinylphenyl group, a 3-vinylphenyl group, a 4-vinylphenyl group, a 2-allylphenyl group, a 3-allylphenyl group and a 4-allylphenyl group, and groups having a substituent such as a 3-allyloxypropyl group or a 3-methacryl- and/or 3-acryloxypropyl group. In view of availability, and reactivity with Sixe2x80x94H groups, a vinyl group is preferred.
Letter symbol b, which represents the number of R2, is a number within the range of 0.01xe2x89xa6bxe2x89xa61. If b less than 0.01, the reaction with Sixe2x80x94H groups does not proceed sufficiently. If b greater than 1, the curability required when the reaction product is added to the silicone resin and the resultant coating film hardness may be insufficient.
The a+b, the total of the organic groups R1 and R2, is a number within the range of 0.5xe2x89xa6a+bxe2x89xa61.8. If a+b less than 0.5, the flexibility to be attained when the product polyorganosiloxane compound of the present invention is added to the silicone resin may be insufficient. If a+b greater than 1.8, the curability required when the polyorganosiloxane compound is added to the silicone resin and the resultant coating film hardness may be insufficient.
The group represented by R3 is at least one member selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms which may have an ether linkage. This is a group corresponding to the ROxe2x80x94Si group of the polyorganosiloxane compound, and is used in the curing with silicone resin when the polyorganosiloxane compound obtained is added to the silicone resin. This group may specifically include a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, an i-butyl group and a Buxe2x80x94Oxe2x80x94C2H4 group. In view of availability, and curability required when the polyorganosiloxane compound of the present invention is added to the silicone resin, a methyl group or an ethyl group is preferred.
Letter symbol c, which represents the number of the group OR3, is a number within the range of 0.01xe2x89xa6cxe2x89xa62.5. If c less than 0.01, the curability required when the product polyorganosiloxane compound of the present invention is added to the silicone resin and the resultant coating film hardness may be insufficient. If c greater than 2.5, the flexibility to be attained when the reaction product is added to the silicone resin may be insufficient.
The a+b+c, the total of all functional groups on Si, is a number within the range of 1xe2x89xa6a+b+cxe2x89xa63. If a+b+c less than 1, the polyorganosiloxane (a1) has so high a molecular weight as to tend to gel. If a+b+c greater than 3, the polyorganosiloxane (a1) has so low a molecular weight as to have a poor compatibility when the polyorganosiloxane compound obtained is added to the silicone resin.
In order to make the polyorganosiloxane (a2) compatible with the silicone resin, the polyorganosiloxane (a1) must have at least some degree of polymerization, and may preferably have an average degree of polymerization (m) of from 2 to 1,000, and more preferably from 5 to 200. If m less than 2, a poor compatibility may result when the polyorganosiloxane compound obtained is added to the silicone resin. If m greater than 1,000, it may be difficult to effect synthesis and also the polyorganosiloxane (a1) may come short of reactivity with the polyorganosiloxane (a2).
Polyorganosiloxane (a2):
The polyorganosiloxane (a2) having a specific structure is a polyorganosiloxane compound represented by the above general formula (2).
This polyorganosiloxane (a2) is a compound commonly called a both-terminal Sixe2x80x94H-group-containing silicone oil, and is known to those skilled in the art.
R1 is as defined in respect of the average compositional formula (1), representing the polyorganosiloxane (a1) and is at least one group selected from the group consisting of a substituted or unsubstituted alkyl group and a substituted or unsubstituted aryl group. Of these, in view of availability, and weatherability or flexibility to be attained when the polyorganosiloxane compound of the present invention is added to the silicone resin, a methyl group is particularly preferred.
In order to improve the flexibility of the silicone resin, this polyorganosiloxane (a2) must also have some degree of polymerization. Accordingly, in the formula (2), n may preferably be from 0 to 1,000, and more preferably from 5 to 200. If n is more than 1,000, the polyorganosiloxane (a2) may come short of reactivity with the polyorganosiloxane (a1) and also a poor compatibility may result when the polyorganosiloxane compound obtained is added to the silicone resin.
Reaction of (a1) with (a2):
In the present invention, the polyorganosiloxane compound is obtained by utilizing the reaction of hydrosilylation of Sixe2x80x94H groups contained in both terminals of the polyorganosiloxane (a2) to aliphatic unsaturated double bonds contained in the polyorganosiloxane (a1). Thus, the polyorganosiloxane compound has a form in which the silicone resin structure of the polyorganosiloxane (a1) having ROxe2x80x94Si groups is bonded to each terminal of the silicone oil straight-chain structure of the polyorganosiloxane (a2).
In this hydrosilylation, a single metal such as Ni, Rh, Pd or Pt or a compound or composite thereof is usually used as a catalyst. In view of good catalytic activity, and also readiness to handle because of a catalyst of uniform system, often used are H2PtCl6.6H2O and an olefin complex of Pt. Also, the catalyst may be used in an effective quantity, which may specifically be in the range of from 0.1 to 1,000 ppm in terms of the metallic element, based on the whole reaction system. These catalysts are expensive and may cause coloring, and hence may preferably be used in a minimum effective quantity necessary for the reaction.
There are no particular limitations on the temperature of this hydrosilylation. Usually, the reaction rate is regulated by heating. Also, in order to dissolve the silicone resin component polyorganosiloxane (a1) and the silicone oil component polyorganosiloxane (a2), having poor compatibility with each other, to make their reaction proceed smoothly, or in order to lower viscosity to make them easy to handle, a solvent such as hexane, pentane, toluene or xylene may be added.
In the present invention, the number of moles of unsaturated double bonds contained in the polyorganosiloxane (a1) and the number of moles of Sixe2x80x94H groups contained in the polyorganosiloxane (a2) may preferably be in a ratio of unsaturated double bond/Sixe2x80x94H group=1 to 10, and more preferably 1.2 to 5. This is because, since polymers react with each other, the presence of one-side functional groups in excess is more advantageous for making them react sufficiently, and also because any unreacted silicone oil component, i.e., unreacted polyorganosiloxane (a2), which may adversely affect the compatibility when the polyorganosiloxane compound obtained is added to the silicone resin can be made not to remain. Also, in the case when the polyorganosiloxane (a1) has two or more unsaturated double bonds in the molecule, this hydrosilylation may cause viscosity build-up and gelation. However, the use of the polyorganosiloxane (a1) in excess can prevent this gelation.
The polyorganosiloxane compound of the present invention may also be obtained by the following process.
Utilizing the reaction of hydrosilylation of Sixe2x80x94H groups to unsaturated groups, a polyorganosiloxane (a3) represented by the average compositional formula (3):
R1dHeSi(OR3)fO(4xe2x88x92dxe2x88x92exe2x88x92f)/2xe2x80x83xe2x80x83(3)
wherein R1 and R3 are as defined in respect of the formula (1); and d, e and f are numbers that satisfy the following relation: 0xe2x89xa6d less than 1.5, 0.01xe2x89xa6exe2x89xa61, 0.5xe2x89xa6d+exe2x89xa61.8, 0.01xe2x89xa6fxe2x89xa62.5 and 1xe2x89xa6d+e+fxe2x89xa63; and having at least one Sixe2x80x94H group in the molecule; is allowed to react with a polyorganosiloxane (a4) represented by the general formula (4): 
wherein R1 and R2 are as defined in respect of the formula (1), and p is a number of from 0 to 1,000.
This polyorganosiloxane (a3) is chiefly composed of R1SiX3 and HSiX3, and is obtained using SiX4, R12SiX2, R13SiX, H2SiX2 and H3SiX [in these formulas, X is as defined previously) in accord with the desired structure, and by hydrolysis and condensation with addition of a solvent and an alcohol (R3OH, where R3 is as defined previously), under acidic or neutral conditions and using water in a quantity smaller than that of water in reaction equivalent weight for the hydrolyzable group X. This compound is known to those skilled in the art, as Sixe2x80x94H-group-containing silicone resin.
The group represented by R1 is as described in respect of the average compositional formula (1), representing the polyorganosiloxane (a1), and is at least one group selected from the group consisting of a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms and a substituted or unsubstituted aryl group having 6 to 20 carbon atoms. Specific examples thereof are also as already described previously, and a methyl group is particularly preferred.
Letter symbol d is a number within the range of 0xe2x89xa6dxe2x89xa61.5. If d greater than 1.5, the curability required when the polyorganosiloxane compound is added to the silicone resin and the resultant coating film hardness may be insufficient.
Letter symbol e is also a number within the range of 0.01xe2x89xa6exe2x89xa61 because the polyorganosiloxane (a3) must have at least one Sixe2x80x94H group in the molecule in order to react with the polyorganosiloxane (a4). If e less than 0.01, the reaction with Sixe2x80x94H groups does not proceed sufficiently. If e greater than 1, the curability required when the reaction product is added to the silicone resin and the resultant coating film hardness may be insufficient.
The d+e, the total of the organic groups R1 and hydrogen atoms, is a number within the range of 0.5xe2x89xa6d+exe2x89xa61.8. If d+e less than 0.5, the flexibility to be attained when the product polyorganosiloxane compound of the present invention is added to the silicone resin may be insufficient. If d+e greater than 1.8, the curability required when the polyorganosiloxane compound is added to the silicone resin and the resultant coating film hardness may be insufficient.
The group represented by R3 is also as described in respect of the formula (1), representing the polyorganosiloxane (a1), and is at least one member selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms which may have an ether linkage. This is a group corresponding to the R3Oxe2x80x94Si group of the polyorganosiloxane compound, and is used in the curing with silicone resin when the polyorganosiloxane compound obtained is added to the silicone resin. Specific examples thereof are also as already described previously, and, in view of the curability required when the polyorganosiloxane compound is added to the silicone resin, a methyl group or an ethyl group is preferred.
Letter symbol f is a number within the range of 0.01xe2x89xa6fxe2x89xa62.5. If f less than 0.01, the curability required when the product polyorganosiloxane compound of the present invention is added to the silicone resin and the resultant coating film hardness may be insufficient. If f greater than 2.5, the flexibility to be attained when the reaction product is added to the silicone resin may be insufficient.
The d+e+f, the total of all functional groups on Si, is a number within the range of 1xe2x89xa6d+e+fxe2x89xa63. If d+e+f less than 1, the polyorganosiloxane (a3) has so high a molecular weight as to tend to gel. If d+e+f greater than 3, the polyorganosiloxane (a3) has so low a molecular weight as to have a poor compatibility when the polyorganosiloxane compound obtained is added to the silicone resin.
In order to make the polyorganosiloxane (a4) compatible with the silicone resin, the polyorganosiloxane (a3) must have at least some degree of polymerization, and may preferably have an average degree of polymerization (q) of from 2 to 1,000, and more preferably from 5 to 200. If q less than 2, a poor compatibility may result when the polyorganosiloxane compound obtained is added to the silicone resin. If q greater than 1,000, it may be difficult to effect synthesis and also the polyorganosiloxane (a3) may come short of reactivity with the polyorganosiloxane (a4).
Polyorganosiloxane (a4):
The polyorganosiloxane (a4) is a polyorganosiloxane represented by the above general formula (4).
This polyorganosiloxane (a4) is a compound commonly called a silicone oil having unsaturated double bonds at both terminals, and is known to those skilled in the art.
R1 is as defined in respect of the formula (1), and is at least one group selected from the group consisting of a substituted or unsubstituted alkyl group and a substituted or unsubstituted aryl group. Specific examples thereof are as exemplified in respect of the formula (1). Of these, in view of availability, and weatherability or flexibility to be attained when the polyorganosiloxane compound of the present invention is added to the silicone resin, a methyl group is particularly preferred.
In order to improve the flexibility of the silicone resin, this polyorganosiloxane (a4) must also have some degree of polymerization. Accordingly, in the formula (4), p may preferably be from 0 to 1,000, and more preferably from 5 to 200. If p greater than 1,000, the polyorganosiloxane (a4) may come short of reactivity with the polyorganosiloxane (a3) and also a poor compatibility may result when the polyorganosiloxane compound obtained is added to the silicone resin.
The organic groups R2 present at the both terminals of the molecule of the polyorganosiloxane (a4) is as defined in respect of the formula (1), and is a group having an aliphatic unsaturated double bond. Specific examples of this group having such an unsaturated double bond are also as exemplified in respect of the formula (1), and, in view of availability, and reactivity with Sixe2x80x94H groups, a vinyl group is preferred.
In the present invention, the polyorganosiloxane compound is obtained by utilizing the reaction of hydrosilylation of Sixe2x80x94H groups contained in the polyorganosiloxane (a3) to aliphatic unsaturated double bonds present at both terminals of the polyorganosiloxane (a4). Thus, the polyorganosiloxane compound has a form in which the silicone resin structure of the polyorganosiloxane (a3) having ROxe2x80x94Si groups is bonded to each terminal of the silicone oil straight-chain structure of the polyorganosiloxane (a4).
In this hydrosilylation, too, the same catalyst as the one described in respect of the polyorganosiloxane compound obtained by the first process is used, and also there are no particular limitations on the reaction temperature and the addition of a solvent.
In the present invention, the number of moles of Sixe2x80x94H groups contained in the polyorganosiloxane (a3) and the number of moles of unsaturated double bonds contained in the polyorganosiloxane (a4) may preferably be in a ratio of Sixe2x80x94H group/unsaturated double bond=1 to 10, and more preferably 1.2 to 5. This is because, since polymers react with each other, the presence of one-side functional groups in excess is more advantageous for making them react sufficiently, and also because any unreacted silicone oil component, i.e., unreacted polyorganosiloxane (a4), which may adversely affect the compatibility when the polyorganosiloxane compound obtained is added to the silicone resin can be made not to remain. Also, in the case when the polyorganosiloxane (a3) has two or more Sixe2x80x94H groups in the molecule, this hydrosilylation may cause viscosity build-up and gelation. However, the use of the polyorganosiloxane (a3) in excess can prevent this gelation.
In the polyorganosiloxane compound according to the present invention, the number (M) of Si atoms of the silicone resin components, i.e., Si atoms due to the polyorganosiloxane (a1) or (a3), and the number (N) of Si atoms of the silicone oil component, i.e., Si atoms due to the polyorganosiloxane (a2) or (a4) may preferably be in a ratio of M/N of from 0.1 to 50, and more preferably from 0.3 to 20. If M/N less than 0.1, the proportion of the silicone resin component is so small that a poor compatibility may result when the polyorganosiloxane compound is added to the silicone resin. Too large a proportion of M/N makes the proportion of the silicone oil component too small to expect any improvement in flexibility when the compound is added to the silicone resin.
In the polyorganosiloxane compound of the present invention, the Si atoms may preferably be in a number of from 5 to 2,000 atoms, and particularly from 10 to 400 atoms.
The polyorganosiloxane compound of the present invention may preferably be a compound in which at least 80 mole % of substituents other than alkoxyl groups and silanol groups contained therein is held by methyl groups. Such a compound is preferred in view of the curability required when the polyorganosiloxane compound is added to the silicone resin and the resultant coating film hardness, flexibility and weatherability.
Coating Composition
The coating composition of the present invention comprises:
(xcex1) from 0.1 part by weight to 100 parts by weight of the polyorganosiloxane compound described above;
(xcex2) from 99.9 parts by weight to 0 part by weight of a silane compound and/or silicone resin containing an R3Oxe2x80x94Si group (R3 is as defined previously);
provided that the total of components (xcex1) and (xcex2) comes to 100 parts by weight; and
(xcex3) from 0.01 part by weight to 50 parts by weight of a curing catalyst, based on 100 parts by weight of the total of the components (xcex1) and (xcex2).
The polyorganosiloxane compound used as component (xcex1) is a component which imparts flexibility to a cured product of this composition. It may be added in an amount of from 0.1 to 100 parts by weight, preferably from 1 to 70 parts by weight, and particularly preferably from 2 to 50 parts by weight. If it is less than 0.1 part by weight, the improvement in flexibility may be insufficient.
The component-(xcex2) silane compound or silicone resin containing an R3Oxe2x80x94Si group, or a mixture of these, is a component that forms a skeletal portion of the coating composition. It is added in an amount of from 99.9 to 0 part by weight, preferably from 99 to 30 parts by weight, and particularly preferably from 98 to 50 parts by weight. If it is more than 99.9 parts by weight, the component-(xcex1) polyorganosiloxane compound is in too small a proportion to expect any improvement in flexibility.
The component-(xcex2) silane compound containing an R3Oxe2x80x94Si group is a component that forms the silicone resin upon hydrolysis and condensation when the coating composition is cured. For example, it may include R4Si(OR3)3, Si(OR3)4, R42Si(OR3)2 and R43SiOR3. Usually, it is composed chiefly of R4Si(OR3)3 and optionally contains at least one of Si(OR3)4, R42Si(OR3)2 and R43SiOR3 in accord with the desired molecular structure.
In the silane compounds exemplified above, the organic group R4 is at least one member selected from the group consisting of a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, a hydrogen atom and a group containing an aliphatic unsaturated double bond. It may specifically include alkyl groups such as a methyl group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, an i-butyl group, a n-decyl group and a n-octadecyl group; aryl groups such as a phenyl group; groups containing a substituent such as a trifluoropropyl group, a perfluorooctylethyl group, a 3-aminopropyl group, a 3-glycidoxypropyl group or a 3-mercaptopropyl group; a hydrogen atom; aliphatic unsaturated groups such as a vinyl group, an allyl group, an isopropenyl group, a 1-butenyl group, a 2-butenyl group and a 3-butenyl group; alicyclic groups such as a 2-cyclohexenyl group, a 3-cyclohexenyl group, a 2-vinylcyclohexyl group, a 3-vinylcyclohexyl group and a 4-vinylcyclohexyl group; aromatic groups such as a 2-vinylphenyl group, a 3-vinylphenyl group, a 4-vinylphenyl group, a 2-allylphenyl group, a 3-allylphenyl group and a 4-allylphenyl group; and groups having a substituent such as a 3-allyloxypropyl group, a 3-methacryloxypropyl group or a polyoxyethylene-containing group. In view of availability, and good curability and weatherability of the coating composition, a methyl group is particularly preferred. Incidentally, different from the polyorganosiloxanes (a1) and (a3), the organic group R4 need not necessarily contain the aliphatic unsaturated double bond or Sixe2x80x94H group.
The R3 in the above silane compound is as defined in respect of the average compositional formula (1), and is at least one member selected from the group consisting of a hydrogen atom and a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms which may have an ether linkage. Specific examples thereof are also as described previously, and, in view of availability, and curability of the coating composition, a methyl group and an ethyl group are preferred.
As examples of such a silane compound, it may specifically include Si(OMe)4, MeSi(OMe)3, Me2Si(OMe)2, Me3SiOMe, Si(OEt)4, MeSi(OEt)3, Me2Si(OEt)2, Me3SiOEt, EtSi(OMe)3, Et2Si(OMe)2, Et3SiOMe, EtSi(OEt)3, Et2Si(OEt)2, Et3SiOEt, n-PrSi(OMe)3, (n-Pr)2Si(OMe)2, (n-Pr)3SiOMe, n-PrSi(OEt)3, (n-Pr)2Si(OEt)2, (n-Pr)3SiOEt, PhSi(OMe)3, Ph2Si(OMe)2, Ph3SiOMe, PhSi(OEt)3, Ph2Si(OEt)2 and Ph3SiOEt, (in these formulas, Me represents a methyl group, Et an ethyl group, n-Pr a n-propyl group and Ph a phenyl group).
The silicone resin containing an R3Oxe2x80x94Si group is a compound represented by the average compositional formula (5):
R4gSi(OR3)hO(4xe2x88x92gxe2x88x92h)/2xe2x80x83xe2x80x83(5)
wherein R3 and R4 are as defined previously, g is a number preferably within the range of 0.5xe2x89xa6gxe2x89xa62.0, and h is a number preferably within the range of 0.01xe2x89xa6hxe2x89xa62.5; and is a compound known to those skilled in the art, as ROxe2x80x94Si-containing silicone resin.
With regard to the organic groups R3 and R4, the R4 may preferably be a methyl group and R3 may preferably be a methyl group or an ethyl group, in view of good curability of the coating composition and good weatherability of cured coatings obtained. Incidentally, different from the polyorganosiloxanes (a1) and (a3), these organic groups need not necessarily contain the unsaturated-double-bond-containing group or Sixe2x80x94H group.
The range of the number represented by g may preferably be, but not particularly limited to, 0.5xe2x89xa6gxe2x89xa62.0. If g is too small, the coating tends to have an insufficient flexibility. If g is too large, the composition may have an insufficient curability, and the resultant coating film an insufficient hardness. The range of the number represented by h may also preferably be, but not particularly limited to, 0.01xe2x89xa6hxe2x89xa62.5. If it is too small, the composition may have an insufficient curability, and the resultant coating film an insufficient hardness. If it is too large, the resultant coating film may have an insufficient flexibility. There are no particular limitations on the average degree of polymerization (r) of this silicone resin, which may usually be from 2 to 1,000 because a silicone resin with r greater than 1,000 may be synthesized with difficulty.
In order to change the viscosity of the coating composition to improve workability or to control the curability of the composition, the hardness and flexibility of the resultant coating film, these silane compound resin containing an R3Oxe2x80x94Si and silicone resin containing an R3Oxe2x80x94Si group may also be used in the form of a mixture.
The curing catalyst (xcex3) is a component which makes the coating composition cure which is obtained by hydrolysis and condensation with water content in air, of R3Oxe2x80x94Si groups contained in the component-(xcex1) polyorganosiloxane compound and the component-(xcex2) silane compound and/or silicone resin containing an R3Oxe2x80x94Si group. It is added in an amount of from 0.01 to 50 parts by weight, and more preferably from 0.05 to 10 parts by weight, based on 100 parts by weight of the total of the components (xcex1) and (xcex2). If it is less than 0.01 part by weight, the composition may have a low curability. Even if it is more than 50 parts by weight, no change can be seen in the curability of the coating composition, resulting in waste or conversely a low curability.
Such a curing catalyst (xcex3) may specifically include acid catalysts such as HCl, H2SO4, H3PO4 and CH3SO3H; alkali metal compounds such as NaOH, KOH, CH3ONa, CH3OK, CH3COONa and CH3COOK; NH3; amine compounds such as EtNH2, Et2NH, Et3N, DBU and H2NC3H6Si(OMe)3; and Al-based, Ti-based or Sn-based metal catalysts such as Al(acac)3, Al(Oxe2x80x94ixe2x80x94Pr)3, Al(ClO4)3, Ti(Oxe2x80x94ixe2x80x94Pr)4, Ti(Oxe2x80x94ixe2x80x94Bu)4, Bu2Sn(acac)2 and Bu2Sn(C7H15COO)2.
The coating composition of the present invention is coated on substrates of various types by known methods such as spraying and brushing, and the curing reaction starts upon its contact with the water content in air. Here, moisture content in air may be enough for the water content. The composition may also positively be brought into contact with water. The curing of this coating composition proceeds well even under conditions of normal temperature, and may also be made by heat treatment at 300xc2x0 C. or below. Especially even when the composition is cured at room temperature as in in situ application, the coating composition of the present invention has so good a curing rate that it becomes not sticky in few hours, promising a good operability. Also, under conditions such that the moisture in air alone may come short of water content as in the case of heat curing, a silicone resin having not only R3Oxe2x80x94Si groups but also Sixe2x80x94OH groups may be used as the component (xcex2), whereby the composition can sufficiently be cured.
When the coating composition of the present invention is used, various additives such as an adhesion improver, an inorganic or organic ultraviolet-light absorber, a storage stability improver, a plasticizer, a filler, an anti-aging agent and a pigment may also be added according to purposes for which the composition is used. Incidentally, the coating composition of the present invention is basically a solvent-free type coating material which is combustible and does not contain any organic solvent harmful to the human body. However, taking account of its uses and operability, a solvent may also be added.
In addition, as the substrates, usable are various metallic materials and workpieces, wood, building stone, slates, mortars, glasses, ceramics, plastic products, tiles, organic resin-coated products and so forth, extending over a wide range of uses.
Usually, the silicone oil component, i.e., the polyorganosiloxane (a2) or (a4) in the case of the present invention is not compatible with the silicone resin (xcex2), and hence any products which are stable and uniform as coating composition can not be obtained. However, in the polyorganosiloxane compound of the present invention, the silicone resin component polyorganosiloxane (a1) or (a3) and the silicone oil component polyorganosiloxane (a2) or (a4) are combined by hydrosilylation, and hence the poor compatibility with the part of the silicone resin component polyorganosiloxane (a1) or (a3) can be avoided. Thus, the cured product of the composition is endowed with flexibility on account of the soft silicone oil structure attributable to the silicone oil component, silicone compound (a2) or (a4). Also, the polyorganosiloxane compound has R3Oxe2x80x94Si groups due to the silicone resin component polyorganosiloxane (a1) or (a3), and participates positively to the curing of this coating composition. Hence, it by no means adversely affects the curing rate and coating film hardness that are characteristic of this coating composition.